malibu 3.1-just changed head gaskets. now it just cranks and backfires??

2000 checy malibu 3.1 I just changed head gaskets. now it won't start. cranks backfires then dies. i have spark and fuel. compression is low around 120-130 so i think i have a vacuum leak to search for.
i have been dealing with this for the last day and think it is time to ask for guidance.
thanks for reading

Crossed wires?

wish it was something that easy. no.
i started tearing back into it and was wondering how to injector o-rings are supposed to seat. the manual reads like they are merely compressed against the hole in the intake as opposed to actually entering the intake.

wish it was something that easy. no.
i started tearing back into it and was wondering how to injector o-rings are supposed to seat. the manual reads like they are merely compressed against the hole in the intake as opposed to actually entering the intake.


the o'rings are on the injector,when you install the fuel rail the injectors
will slide into the manifold (hole).make sure you lube o'rings. they will seat/seal inside hole via the o'ring.

how did engine run before? no sure if the 3.1 has differant intake/exhaust push rods. worth checking

i have it down to where i can get the covers off so will probably go ahead and check the pushrods this morning- they are different sizes though i was careful to make sure i did not mix them up.

it ran fine before i changed the gaskets (other than overheating ).

every place has the fuel o-rings i bought as the correct replacements, though they seem larger than the ones i took off. maybe the the old rings just seem smaller cuz they are old? so i never had the new ones seated in the holes. THAT IS PROBABLY MY LEAK! guess i will coat them with oil and get them installed today. they just seem like they don't want to go in.

Lite coat of vasoline will do it.

tore back into it pretty deep today. i am thinking i had the rocker arms way over torqued to the wrong specs. would that cause the valves to stick and therefore misfire and not start??

Got compression, you say so, so not a valve issue.

if the valves were sticking compression would be 0 ? cuz i do have compression but it is pretty low.

Could just be low from not holding the throttle open or low cranking rpms.

The intake pushroods are 5 3/4 inches long and should have a yellow stripe.
The exhaust pushrod is 6 inches long and should have a green stripe.
If these get mixed up the long ones will usually bend. I would definately check this after the basic crossed wires. vacuum leaks etc. If the long rod got put on the intake and bent low compression could be a result. Bent pushrods will cause backfiring also.